/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, Sandia National Laboratories
   LAMMPS development team: developers@lammps.org

   Copyright (2003) Sandia Corporation.  Under the terms of Contract
   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
   certain rights in this software.  This software is distributed under
   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */

/* ----------------------------------------------------------------------
   Contributing author: Trung Dac Nguyen (Northwestern)
------------------------------------------------------------------------- */

#include "pair_lj_cut_dipole_long_gpu.h"

#include "atom.h"
#include "domain.h"
#include "error.h"
#include "ewald_const.h"
#include "force.h"
#include "gpu_extra.h"
#include "kspace.h"
#include "math_const.h"
#include "neigh_list.h"
#include "neighbor.h"
#include "suffix.h"
#include "update.h"

#include <cmath>
#include <cstring>

using namespace LAMMPS_NS;
using namespace MathConst;
using namespace EwaldConst;

// External functions from cuda library for atom decomposition

int dplj_gpu_init(const int ntypes, double **cutsq, double **host_lj1, double **host_lj2,
                  double **host_lj3, double **host_lj4, double **offset, double *special_lj,
                  const int nlocal, const int nall, const int max_nbors, const int maxspecial,
                  const double cell_size, int &gpu_mode, FILE *screen, double **host_cut_ljsq,
                  const double host_cut_coulsq, double *host_special_coul, const double qqrd2e,
                  const double g_ewald);
void dplj_gpu_clear();
int **dplj_gpu_compute_n(const int ago, const int inum, const int nall, double **host_x,
                         int *host_type, double *sublo, double *subhi, tagint *tag, int **nspecial,
                         tagint **special, const bool eflag, const bool vflag, const bool eatom,
                         const bool vatom, int &host_start, int **ilist, int **jnum,
                         const double cpu_time, bool &success, double *host_q, double **host_mu,
                         double *boxlo, double *prd);
void dplj_gpu_compute(const int ago, const int inum, const int nall, double **host_x,
                      int *host_type, int *ilist, int *numj, int **firstneigh, const bool eflag,
                      const bool vflag, const bool eatom, const bool vatom, int &host_start,
                      const double cpu_time, bool &success, double *host_q, double **host_mu,
                      const int nlocal, double *boxlo, double *prd);
double dplj_gpu_bytes();

/* ---------------------------------------------------------------------- */

PairLJCutDipoleLongGPU::PairLJCutDipoleLongGPU(LAMMPS *lmp) :
    PairLJCutDipoleLong(lmp), gpu_mode(GPU_FORCE)
{
  respa_enable = 0;
  reinitflag = 0;
  cpu_time = 0.0;
  suffix_flag |= Suffix::GPU;
  GPU_EXTRA::gpu_ready(lmp->modify, lmp->error);
}

/* ----------------------------------------------------------------------
   free all arrays
------------------------------------------------------------------------- */

PairLJCutDipoleLongGPU::~PairLJCutDipoleLongGPU()
{
  dplj_gpu_clear();
}

/* ---------------------------------------------------------------------- */

void PairLJCutDipoleLongGPU::compute(int eflag, int vflag)
{
  ev_init(eflag, vflag);

  int nall = atom->nlocal + atom->nghost;
  int inum, host_start;

  bool success = true;
  int *ilist, *numneigh, **firstneigh;
  if (gpu_mode != GPU_FORCE) {
    double sublo[3], subhi[3];
    if (domain->triclinic == 0) {
      sublo[0] = domain->sublo[0];
      sublo[1] = domain->sublo[1];
      sublo[2] = domain->sublo[2];
      subhi[0] = domain->subhi[0];
      subhi[1] = domain->subhi[1];
      subhi[2] = domain->subhi[2];
    } else {
      domain->bbox(domain->sublo_lamda, domain->subhi_lamda, sublo, subhi);
    }
    inum = atom->nlocal;
    firstneigh = dplj_gpu_compute_n(neighbor->ago, inum, nall, atom->x, atom->type, sublo, subhi,
                                    atom->tag, atom->nspecial, atom->special, eflag, vflag,
                                    eflag_atom, vflag_atom, host_start, &ilist, &numneigh, cpu_time,
                                    success, atom->q, atom->mu, domain->boxlo, domain->prd);
  } else {
    inum = list->inum;
    ilist = list->ilist;
    numneigh = list->numneigh;
    firstneigh = list->firstneigh;
    dplj_gpu_compute(neighbor->ago, inum, nall, atom->x, atom->type, ilist, numneigh, firstneigh,
                     eflag, vflag, eflag_atom, vflag_atom, host_start, cpu_time, success, atom->q,
                     atom->mu, atom->nlocal, domain->boxlo, domain->prd);
  }
  if (!success) error->one(FLERR, "Insufficient memory on accelerator");

  if (atom->molecular != Atom::ATOMIC && neighbor->ago == 0)
    neighbor->build_topology();
  if (host_start < inum) {
    cpu_time = platform::walltime();
    cpu_compute(host_start, inum, eflag, vflag, ilist, numneigh, firstneigh);
    cpu_time = platform::walltime() - cpu_time;
  }
}

/* ----------------------------------------------------------------------
   init specific to this pair style
------------------------------------------------------------------------- */

void PairLJCutDipoleLongGPU::init_style()
{
  if (!atom->q_flag || !atom->mu_flag || !atom->torque_flag)
    error->all(FLERR, "Pair dipole/cut/gpu requires atom attributes q, mu, torque");

  if (strcmp(update->unit_style, "electron") == 0)
    error->all(FLERR, "Cannot (yet) use 'electron' units with dipoles");

  // Repeat cutsq calculation because done after call to init_style
  double maxcut = -1.0;
  double cut;
  for (int i = 1; i <= atom->ntypes; i++) {
    for (int j = i; j <= atom->ntypes; j++) {
      if (setflag[i][j] != 0 || (setflag[i][i] != 0 && setflag[j][j] != 0)) {
        cut = init_one(i, j);
        cut *= cut;
        if (cut > maxcut) maxcut = cut;
        cutsq[i][j] = cutsq[j][i] = cut;
      } else
        cutsq[i][j] = cutsq[j][i] = 0.0;
    }
  }
  double cell_size = sqrt(maxcut) + neighbor->skin;

  cut_coulsq = cut_coul * cut_coul;

  // ensure use of KSpace long-range solver, set g_ewald

  if (force->kspace == nullptr) error->all(FLERR, "Pair style requires a KSpace style");
  g_ewald = force->kspace->g_ewald;

  // setup force tables

  if (ncoultablebits) init_tables(cut_coul, nullptr);

  int maxspecial = 0;
  if (atom->molecular != Atom::ATOMIC) maxspecial = atom->maxspecial;
  int mnf = 5e-2 * neighbor->oneatom;
  int success =
      dplj_gpu_init(atom->ntypes + 1, cutsq, lj1, lj2, lj3, lj4, offset, force->special_lj,
                    atom->nlocal, atom->nlocal + atom->nghost, mnf, maxspecial, cell_size, gpu_mode,
                    screen, cut_ljsq, cut_coulsq, force->special_coul, force->qqrd2e, g_ewald);
  GPU_EXTRA::check_flag(success, error, world);

  if (gpu_mode == GPU_FORCE) neighbor->add_request(this, NeighConst::REQ_FULL);
}

/* ---------------------------------------------------------------------- */

double PairLJCutDipoleLongGPU::memory_usage()
{
  double bytes = Pair::memory_usage();
  return bytes + dplj_gpu_bytes();
}

/* ---------------------------------------------------------------------- */

void PairLJCutDipoleLongGPU::cpu_compute(int start, int inum, int eflag, int vflag, int *ilist,
                                         int *numneigh, int **firstneigh)
{
  int i, j, ii, jj, jnum, itype, jtype;
  double qtmp, xtmp, ytmp, ztmp, delx, dely, delz;
  double rsq, r, rinv, r2inv, r6inv;
  double forcecoulx, forcecouly, forcecoulz, fforce;
  double tixcoul, tiycoul, tizcoul;
  double fx, fy, fz, fdx, fdy, fdz, fax, fay, faz;
  double pdotp, pidotr, pjdotr, pre1, pre2, pre3;
  double grij, expm2, t, erfc;
  double g0, g1, g2, b0, b1, b2, b3, d0, d1, d2, d3;
  double zdix, zdiy, zdiz, zaix, zaiy, zaiz;
  double g0b1_g1b2_g2b3, g0d1_g1d2_g2d3;
  double forcelj, factor_coul, factor_lj, facm1;
  double evdwl, ecoul;
  int *jlist;

  evdwl = ecoul = 0.0;
  ev_init(eflag, vflag);

  double **x = atom->x;
  double **f = atom->f;
  double *q = atom->q;
  double **mu = atom->mu;
  double **torque = atom->torque;
  int *type = atom->type;
  double *special_coul = force->special_coul;
  double *special_lj = force->special_lj;
  double qqrd2e = force->qqrd2e;

  pre1 = 2.0 * g_ewald / MY_PIS;
  pre2 = 4.0 * pow(g_ewald, 3.0) / MY_PIS;
  pre3 = 8.0 * pow(g_ewald, 5.0) / MY_PIS;

  // loop over neighbors of my atoms

  for (ii = start; ii < inum; ii++) {
    i = ilist[ii];
    qtmp = q[i];
    xtmp = x[i][0];
    ytmp = x[i][1];
    ztmp = x[i][2];
    itype = type[i];
    jlist = firstneigh[i];
    jnum = numneigh[i];

    for (jj = 0; jj < jnum; jj++) {
      j = jlist[jj];
      factor_lj = special_lj[sbmask(j)];
      factor_coul = special_coul[sbmask(j)];
      j &= NEIGHMASK;

      delx = xtmp - x[j][0];
      dely = ytmp - x[j][1];
      delz = ztmp - x[j][2];
      rsq = delx * delx + dely * dely + delz * delz;
      jtype = type[j];

      if (rsq < cutsq[itype][jtype]) {
        r2inv = 1.0 / rsq;
        rinv = sqrt(r2inv);

        if (rsq < cut_coulsq) {
          r = sqrt(rsq);
          grij = g_ewald * r;
          expm2 = exp(-grij * grij);
          t = 1.0 / (1.0 + EWALD_P * grij);
          erfc = t * (A1 + t * (A2 + t * (A3 + t * (A4 + t * A5)))) * expm2;

          pdotp = mu[i][0] * mu[j][0] + mu[i][1] * mu[j][1] + mu[i][2] * mu[j][2];
          pidotr = mu[i][0] * delx + mu[i][1] * dely + mu[i][2] * delz;
          pjdotr = mu[j][0] * delx + mu[j][1] * dely + mu[j][2] * delz;

          g0 = qtmp * q[j];
          g1 = qtmp * pjdotr - q[j] * pidotr + pdotp;
          g2 = -pidotr * pjdotr;

          if (factor_coul > 0.0) {
            b0 = erfc * rinv;
            b1 = (b0 + pre1 * expm2) * r2inv;
            b2 = (3.0 * b1 + pre2 * expm2) * r2inv;
            b3 = (5.0 * b2 + pre3 * expm2) * r2inv;

            g0b1_g1b2_g2b3 = g0 * b1 + g1 * b2 + g2 * b3;
            fdx = delx * g0b1_g1b2_g2b3 - b1 * (qtmp * mu[j][0] - q[j] * mu[i][0]) +
                b2 * (pjdotr * mu[i][0] + pidotr * mu[j][0]);
            fdy = dely * g0b1_g1b2_g2b3 - b1 * (qtmp * mu[j][1] - q[j] * mu[i][1]) +
                b2 * (pjdotr * mu[i][1] + pidotr * mu[j][1]);
            fdz = delz * g0b1_g1b2_g2b3 - b1 * (qtmp * mu[j][2] - q[j] * mu[i][2]) +
                b2 * (pjdotr * mu[i][2] + pidotr * mu[j][2]);

            zdix = delx * (q[j] * b1 + b2 * pjdotr) - b1 * mu[j][0];
            zdiy = dely * (q[j] * b1 + b2 * pjdotr) - b1 * mu[j][1];
            zdiz = delz * (q[j] * b1 + b2 * pjdotr) - b1 * mu[j][2];

            if (factor_coul < 1.0) {
              fdx *= factor_coul;
              fdy *= factor_coul;
              fdz *= factor_coul;
              zdix *= factor_coul;
              zdiy *= factor_coul;
              zdiz *= factor_coul;
            }
          } else {
            fdx = fdy = fdz = 0.0;
            zdix = zdiy = zdiz = 0.0;
          }

          if (factor_coul < 1.0) {
            d0 = (erfc - 1.0) * rinv;
            d1 = (d0 + pre1 * expm2) * r2inv;
            d2 = (3.0 * d1 + pre2 * expm2) * r2inv;
            d3 = (5.0 * d2 + pre3 * expm2) * r2inv;

            g0d1_g1d2_g2d3 = g0 * d1 + g1 * d2 + g2 * d3;
            fax = delx * g0d1_g1d2_g2d3 - d1 * (qtmp * mu[j][0] - q[j] * mu[i][0]) +
                d2 * (pjdotr * mu[i][0] + pidotr * mu[j][0]);
            fay = dely * g0d1_g1d2_g2d3 - d1 * (qtmp * mu[j][1] - q[j] * mu[i][1]) +
                d2 * (pjdotr * mu[i][1] + pidotr * mu[j][1]);
            faz = delz * g0d1_g1d2_g2d3 - d1 * (qtmp * mu[j][2] - q[j] * mu[i][2]) +
                d2 * (pjdotr * mu[i][2] + pidotr * mu[j][2]);

            zaix = delx * (q[j] * d1 + d2 * pjdotr) - d1 * mu[j][0];
            zaiy = dely * (q[j] * d1 + d2 * pjdotr) - d1 * mu[j][1];
            zaiz = delz * (q[j] * d1 + d2 * pjdotr) - d1 * mu[j][2];

            if (factor_coul > 0.0) {
              facm1 = 1.0 - factor_coul;
              fax *= facm1;
              fay *= facm1;
              faz *= facm1;
              zaix *= facm1;
              zaiy *= facm1;
              zaiz *= facm1;
            }
          } else {
            fax = fay = faz = 0.0;
            zaix = zaiy = zaiz = 0.0;
          }

          forcecoulx = fdx + fax;
          forcecouly = fdy + fay;
          forcecoulz = fdz + faz;

          tixcoul = mu[i][1] * (zdiz + zaiz) - mu[i][2] * (zdiy + zaiy);
          tiycoul = mu[i][2] * (zdix + zaix) - mu[i][0] * (zdiz + zaiz);
          tizcoul = mu[i][0] * (zdiy + zaiy) - mu[i][1] * (zdix + zaix);
        } else {
          forcecoulx = forcecouly = forcecoulz = 0.0;
          tixcoul = tiycoul = tizcoul = 0.0;
        }

        // LJ interaction

        if (rsq < cut_ljsq[itype][jtype]) {
          r6inv = r2inv * r2inv * r2inv;
          forcelj = r6inv * (lj1[itype][jtype] * r6inv - lj2[itype][jtype]);
          fforce = factor_lj * forcelj * r2inv;
        } else
          fforce = 0.0;

        // total force

        fx = qqrd2e * forcecoulx + delx * fforce;
        fy = qqrd2e * forcecouly + dely * fforce;
        fz = qqrd2e * forcecoulz + delz * fforce;

        // force & torque accumulation

        f[i][0] += fx;
        f[i][1] += fy;
        f[i][2] += fz;
        torque[i][0] += qqrd2e * tixcoul;
        torque[i][1] += qqrd2e * tiycoul;
        torque[i][2] += qqrd2e * tizcoul;

        if (eflag) {
          if (rsq < cut_coulsq && factor_coul > 0.0) {
            ecoul = qqrd2e * (b0 * g0 + b1 * g1 + b2 * g2);
            if (factor_coul < 1.0) {
              ecoul *= factor_coul;
              ecoul += (1 - factor_coul) * qqrd2e * (d0 * g0 + d1 * g1 + d2 * g2);
            }
          } else
            ecoul = 0.0;

          if (rsq < cut_ljsq[itype][jtype]) {
            evdwl = r6inv * (lj3[itype][jtype] * r6inv - lj4[itype][jtype]) - offset[itype][jtype];
            evdwl *= factor_lj;
          } else
            evdwl = 0.0;
        }

        if (evflag) ev_tally_xyz_full(i, evdwl, ecoul, fx, fy, fz, delx, dely, delz);
      }
    }
  }
}
